The present invention relates to an improved molded muffler formed of a polymeric material.
A variety of mufflers have been designed to reduce the noise output related to the exhaust from internal combustion engines. Traditionally, mufflers are formed of a metal shell which encases a variety of baffles walls or interconnected chambers. These metal mufflers are highly susceptible to corrosion largely the result of acids which condense within the muffler.
There have been a variety of attempts to overcome the corrosion problems of a metal muffler. One such attempt is disclosed in U.S. Pat. No. 3,638,756 issued Feb. 1, 1972 to Thiele. Thiele discloses a stamped metal muffler constructed by bonding top and bottom muffler halves along only their outside edge by welding, adhesive or brazing. The top and bottom pieces are stamped to create a series of mixing chambers within the muffler. Thiele suggests that the two muffler halves may be molded of plastic (column 1, lines 59-62), but does not suggest how this might be accomplished. Thiele contends that corrosion is largely the result of bare metal edges exposed to corrosive elements within the interior of the muffler. Thiele further asserts that stamped construction will largely overcome this problem as it eliminates bare metal edges within the muffler's interior. The disclosed Thiele muffler is metal and therefore subject to corrosion.
A more successful way to address the problem of corrosion is to provide a muffler formed of plastic. A vibratory flexible silencer formed by bonding two halves fashioned of an elastomer or plastic material is disclosed in U.S. Pat. No. 2,859,830 issued Nov. 11, 1958 to Hoffar. A number of damper walls are positioned within the silencer body. The damper walls are designed to be slightly shorter than the exterior wall of the silencer. This creates a narrow slit through which the exhaust gas may flow when the two halves are joined. These gas flow slits lie along the plane of contact between the two muffler halves. The muffler halves are joined about their perimeters only. Further, all of the gas flow openings intersect a single plane, thereby weakening the overall structure of the muffler.
It is also desirable to reduce the pollution caused by automobile exhaust by converting otherwise harmful exhaust into primarily harmless products. Typically, this is done by means of a catalytic converter located in the exhaust assembly upstream and separate from the muffler. The typical catalytic converter is housed in a metal shell susceptible to corrosion as discussed above. Further, maintenance and replacement of a catalytic converter is relatively expensive and labor intensive.